1. Field of the Invention
The current invention is concerned with position sensing of a remote target and has particular, but not exclusive, relevance to the computer industry.
2. Discussion of Prior Art
The computer industry is a rapidly evolving area of technology where manufacturers are constantly seeking innovations which will provide an advantage over competitors products. One particular area which is the object of much attention is the Human Computer Interface (HCI) or Man Machine Interface, that is, the means by which the computer operator communicates with the computer, inputting data and commands and receiving information.
The use of menu driven and windowing software greatly enhances the user friendliness of many computer related products, especially if such software is used in conjunction with a computer mouse or trackerball. These are handheld devices which allow the user to interact with software/hardware by moving a graphical pointer around on a computer screen, making selections from displayed options, manipulating software windows, drawing etc. by moving the mouse over a surface or operating the tracker ball by thumb motion and taking action by depressing a button.
A particular application of the current invention offers a system where the handheld mouse is redundant and the pointer on screen moves in response to movements of the operators head. This leaves both hands free to operate the keyboard which is particularly advantageous to, for example, typists.
The control of the cursor by movements of the operators head is very ergonomic and intuitive. The equivalent to depressing the mouse button may be achieved either by additional buttons on the keyboard or by detection of specific head movements such as a shake or nod. This may be achieved without the need for any wires, batteries or other impedimenta on the operator and may be implemented at a cost comparable to the existing mouse.
There are various ways in which the motion of the operators head can be used to control the cursor position on the screen.
Firstly, the motion of the head and the cursor may be locked together exactly, regardless of the speed of motion of the head. This is an absolute mode and is used in the implementation described in this specification.
Secondly, the motion of the head and cursor may be coupled in a manner dependent on both the position and speed of motion of the head. This is a relative mode and is the speed sensitive option available with some mouse systems. Slow movement of the head by one cm corresponds to movement of the cursor by one centimeter while rapid movement of the head by one cm results in say four cm of cursor movement. This option would be available with the system described and could be implemented in software or hardware.
Thirdly, the cursor may move only in response to motion of the head and not the absolute position of the head. The absolute head position can be extracted when a signal is present, but that signal is only present during motion.
Many other applications of the invention are envisaged: by exploiting the retroreflecting properties of the human eye, eye movements may be sensed to ensure that the driver of a vehicle is not falling asleep; the invention may be used to track objects other than the operators head; by movement of hand or foot or limb stump, disabled persons may control software driven apparatus carrying out any number of tasks; eye movement and head movement scanned in combination will allow gaze direction information to be extracted; in industry, process control in a dirty environment could be effected with the hands free; a pair systems of the invention could be used to obtain two directional fixes on a target, allowing the position in three dimensions to be established.